They lost in eastern conference semi-finals, not ECF.
That’s why nobody remembers them, they didn’t do anything significant. Clearly, even you weren’t paying attention.
The Celtics team that Wizards lost too lost 4-1 in ECF to Cavs.
At the time, it was Cavs as the best team in the conference followed by above average teams like Raps, Celtics, Bucks, Sixers and Wizards. The Wizards failed to standout among these teams.
It also takes time for the United effect to kick in.